1. Technical Field
The present invention relates to a glass base material elongating method.
2. Related Art
A glass rod with a small diameter such as an optical fiber preform is manufactured by first manufacturing a large-sized glass base material, and then elongating the glass base material. The glass base material is elongated by pulling a pulling dummy that is connected to an end of the glass base material. Japanese Patent No. 4395061 describes that when an optical fiber base material is elongated using a horizontal glass lathe, rough surface parts are provided at parts of dummy rods at both the ends of the optical fiber base material at which the dummy rods are gripped by chucks to prevent slipping between the dummy rods and the chucks. Japanese Patent No. 4471857 describes that a heat-resistant woven fabric is wound around a pulling roller to reduce slipping between the pulling roller and a glass rod.
In the beginning of elongation when elongation of a glass base material is just started, a pulling dummy is pulled with a significant pulling force. Accordingly, in the beginning of elongation, slipping may occur between a pulling roller and a glass base material.